
Introduction. The unique controllability of ultracold atomic and molecular collisions [1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]} gives rise to numerous applications of ultracold quantum gases in quantum information science and on precision tests of foundations of chemical and statistical physics [5]}, [12]}.
Further, much progress has been achieved over the last few years in our ability to observe the reactants and products of molecular collisions and chemical reactions in single, well-controlled quantum states [6]}, [7]}, [8]}, [9]}, [12]}. Recent examples include precision studies of photoexcited reaction complexes [9]} and product state distributions [12]} in the ultracold chemical reaction KRb + KRb \(\rightarrow \)  K\(_2\)  + Rb\(_2\) ,
electric field-induced dipolar exchange resonances in KRb + KRb collisions [7]}, and microwave shielding of NaK + NaK collisions [8]}. In addition, observations have been made of ultracold atom-molecule collisions in an optically trapped Na - NaLi(\(^3\Sigma \) ) mixture, of CaF\((^2\Sigma )\)  + CaF\((^2\Sigma )\)  collisions in an optical dipole trap [22]} and of cold O\(_2(^3\Sigma )\)  + O\(_2(^3\Sigma )\)  collisions in a magnetically trapped gas of oxygen molecules [23]}.
